I've got the same 245/40/18 Goodyear NCT5 RFT tires all around. The one in the front has a bubble on the sidewall, and is at 6/32 tread. A new tire has 10/32 tread. So if I get it replaced under warranty, I'll have one on the front that's 6/32 and another that's 10/32.

I've read Audi says a difference of up to 4/32 is ok? If it is ok, I'll put the new one on the rear anyway, and bring the rear up, so I'll have one 9/32 and one 6/32 on the front, and a 10/32 and 9/32 in the back.

Does it matter which side in the front gets the 9/32? (i.e. is it better on driver's or passenger)

If the difference is too big, I'll probably just buy a used one if I can find one, rather than a new and shave it to match the other.
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But it got me thinking, what is the best plan? Get a new tire for half price or so (there's a prorated warranty on these), in which case I'd have two at 9/32, one at 10/32, and one at 6/32?

Or get a used one around 6/32 where I'd end up with two at 9/32 and two at 6/32. Then my fronts would run out and I'd have two on the rear still at 5/32 (assume even wear).

Maybe I'm better off getting a new one now, and then when the one remaining "old" front wears down, hope I can find a used one that matches the other 3 that might be around 5/32 then, so I can get full use out of them?

This sucks and is giving me a headache!

Thanks for your help!

 

I think you'll be fine replacing the defective tire...4/32nds isn't a big difference. If it'd make you feel better see if the dealer will also adjust the other tire so you have a matched pair.

 

You mean under warranty, get the other front replaced? They won't... I tried. I'd have to pay out of pocket like $500 now.

So if it's fine, you'd leave it as is, then when the current old one on the front needs replacement, and the other three tires are still at 5/32, you'd get just one new one? Or a used at the time? There's no way at that point I'd replace all 4 tires...

 

at 5/32 your tires will be at just under 4mm, minimum SAFE level is 3mm, Personally I would replace them then.

 

Right, I understand that at 4/32 (3 mm) it's considered the time to swap them out for safety in rain, even though the legal limit is 2/32 (1.6 mm). I don't know when I've replaced tires in the past (didn't use to have a gauge) but it was before I'd reached the wear bar on the tire, which I presume is at 2/32.
I ended up finding a used tire at 8/32 tread (6.35 mm), so decided to warranty the one with the bubble, and put this almost new one on. Then I'll keep the used one that will be left just in case...